Other finger models have been made to be manipulated for demonstration purposes but none, to the knowledge of the applicant, has had the interconnections of the various tendons that the present model possesses. The principal deficiency of prior art models has been the limitation to single or joint functions with at best only partial inter-tendonal or inter-joint capabilities. This is true also where artificial hand models have been provided.
The primary advantage of the present model relates to the interconnections of the simulated tendon cords. For example, the extensor and intrinsic cords are interconnected in two different respects so that the distal interphalangeal and proximal interphalangeal joints may be extended only by tensing the extensor cord along with the intrinsic cord. The finger model was built primarily to demonstrate this unique feature.
Another feature of the present invention is that there is an elastic means tending to urge the metacarpophalangeal joint into extended position but permitting that joint to overextend to a certain extent in such wise that a greater movement of the joint can be obtained when it is extended. Also a feature is the presence of an elastic means at the proximal interphalangeal joint that tends to apply a restorative extensor force to that joint tending to return it from a flexed position.
Another feature is that some of the tendon cords are connected by removable connections so that they may be readily disconnected to demonstrate abnormalities caused by injury or disease.
Other objects include the provision of simulated sublimis and profundus tendon cords, especially in combination with the foregoing tendon cords. The sublimis tendon cord is designed to operate most particularly the proximal interphalangeal joint between the middle and first phalanges, with tunnels or tendon sheaths simulating those features of the human hand. The profundus tendon cord is particularly adapted to control the distal interphalangeal joint between the distal and middle phalanges and likewise has appropriate tunnel or tendon sheaths that cause it to simulate the action of the profundus tendon of the human hand.
All of these major cords, namely, the simulated intrinsic or I cord, simulated sublimis of S cord, the simulated profundus or P cord, and the simulated extensor or E cord, are all brought to a location with respect to the model that enables them to be operated by the fingers of the demonstrator to show normal and abnormal functions of the finger.
The fuller description to follow will show other advantages of this model.